--- unif.c.~1.192.2.2.~	2006-02-14 08:59:03.000000000 +1100
+++ unif.c	2006-02-25 18:22:35.000000000 +1100
@@ -380,9 +380,9 @@
   pos += scm_array_handle_bit_elements_offset (h);
   mask = 1l << (pos % 32);
   if (scm_to_bool (val))
-    ((scm_t_uint32 *)h->elements)[pos/32] |= mask;
+    ((scm_t_uint32 *)h->writable_elements)[pos/32] |= mask;
   else
-    ((scm_t_uint32 *)h->elements)[pos/32] &= ~mask;
+    ((scm_t_uint32 *)h->writable_elements)[pos/32] &= ~mask;
 }
 
 static void